Data storage devices are used in a variety of applications to store and retrieve user data. The data are often stored to internal storage media, such as one or more rotatable discs accessed by an array of data transducers that are moved to different radii of the media to carry out I/O operations with tracks defined thereon.
Sort strategies can be used to promote the servicing of I/O requests in a particular radial vicinity of the media. While this can improve overall data throughput rates, some data requests can become undesirably delayed, or “back watered,” as the locus of activity is moved away from the radial position of such requests.
Back watered requests thus remain pending for execution, but are bypassed in favor of other, more efficiently executable requests. From a host or controller point of view, however, back watered requests are generally indistinguishable from “lost” requests that were never successfully received by the device in the first place.